Blur is one of the most important features related to video quality. Accurately estimating the blur level of a video is a great help to accurately evaluate the video quality. However, the perceptual blur level is influenced by many factors such as texture, luminance, etc. Moreover, the blur generated by compression is much different from the blur in the original sequences, such as out-of-focus blur and motion blur. It is difficult to accurately estimate the blur level of a video. Various methods have been proposed to solve the problem. Those methods try to estimate the blur level of a video/image from different aspects, however the performance is not satisfying, especially for different arbitrary video content. E.g. WO03092306 detects local minimum and maximum pixels closest to a current position. That is, if there are two or more neighbouring pixels with same luminance value, it uses the pixel closest to the position.